Recyclable hard cross-linked polyvinyl chloride foam material and preparation method thereof

Abstract

The invention belongs to the technical field of foam materials, and particularly relates to a recyclable hard cross-linked polyvinyl chloride foam material and a preparation method thereof, and the formula comprises 100 parts of polyvinyl chloride, 30-80 parts of epoxy resin, 10-30 parts of a chain extender, 10-30 parts of a reversible curing agent, 10-20 parts of a plasticizer, 10-30 parts of a foaming agent, and 5-10 parts of a nucleating agent. The foam material disclosed by the invention is short in production period, high in mechanical strength, low in glue absorption amount and recyclable.

Description

Technical Field

[0001] The invention belongs to the technical field of foam materials, and in particular relates to a recyclable rigid cross-linked polyvinyl chloride foam material and a preparation method thereof. Background Art

[0002] Rigid cross-linked polyvinyl chloride foam is one of the main core materials for wind turbine blades. Due to its own production process characteristics, thermosetting characteristics and core material processing characteristics, the production cycle of rigid cross-linked polyvinyl chloride core material exceeds 15 days, the material utilization rate is less than 60%, and the foam cells are coarse. Long production cycle, low material utilization rate, high solid waste treatment cost, and large amount of glue absorption are technical problems that the polyvinyl chloride core material industry has not been able to solve for a long time. Although there are patent reports that polyvinyl chloride foam solid waste can be crushed, glued, and compressed to make artificial boards, its manufacturing cost is much higher than that of traditional artificial boards, and it has no competitive advantage at all and cannot solve the solid waste problem. Summary of the invention

[0003] The present invention aims to provide a recyclable rigid cross-linked polyvinyl chloride foam material and a preparation method thereof, so as to solve the problems of low material utilization, high solid waste treatment cost, long production cycle and large amount of glue absorption in the prior art.

[0004] In order to achieve the purpose, the present invention adopts the following technical scheme:

[0005] The present invention first provides a recyclable rigid cross-linked polyvinyl chloride foam material, the raw materials of which are composed of the following components in terms of mass fraction:

[0006]

[0007] Preferably, the polyvinyl chloride is a PVC resin with a degree of polymerization of 1000-5000.

[0008] Preferably, the epoxy resin is at least one of bisphenol A epoxy resin, bisphenol F epoxy resin and bisphenol S epoxy resin with a viscosity of 1000 to 20000 mPa·s.

[0009] Preferably, the chain extender is a compound with a chemical structure as shown in formula (1), wherein R1 is C1 to C 20 At least one of an alkane, an arene, and a cycloalkane group:

[0010]

[0011] Preferably, the plasticizer is at least one of epoxy soybean oil, epoxy methyl ester, and epoxy fatty acid methyl ester.

[0012] Preferably, the foaming agent is at least one of cyclopentane, carbon dioxide and nitrogen.

[0013] Preferably, the reversible curing agent is at least one of maleimide compounds containing not less than 2 maleimide groups and having a molecular weight of 200 to 12,000.

[0014] Preferably, the nucleating agent is at least one of titanium dioxide, calcium carbonate, magnesium carbonate, and silicon dioxide having a particle size not greater than 10 microns.

[0015] The present invention also provides a method for preparing the above recyclable rigid cross-linked polyvinyl chloride foam material, which is carried out according to the following steps:

[0016] S1: The chain extender is uniformly added dropwise into the reaction kettle containing epoxy resin within 1 - 3 h and reacted at a temperature of 20 - 40 °C to obtain modified epoxy resin;

[0017] S2: The raw materials except the foaming agent are fed into the screw extruder through the first feeding port of the automatic feeding machine, and the mixing temperature of the first mixing section of the screw extruder is controlled between 180 - 200 °C;

[0018] S3: The foaming agent is pressurized to 5 - 15 Mpa and then fed into the screw extruder through the second feeding port, and the mixing temperature of the second mixing section of the screw extruder is controlled between 150 - 180 °C;

[0019] S4: The die temperature of the screw extruder is controlled at 110 - 140 °C, and the extruded material is expanded and foamed;

[0020] S5: The expanded foam is sent into a drying channel at 90 - 110 °C through a conveyor belt and cured for 1 - 3 h to obtain the product.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) By bypassing the isocyanate production route and adopting the supercritical foaming molding process, the production cycle is shortened from more than ten days to several hours, the production efficiency is significantly improved, and the production energy consumption is significantly reduced.

[0023] (2) There is only a requirement for the degree of polymerization of the polyvinyl chloride raw material, and expensive emulsifying powder does not need to be used, so the cost is greatly reduced.

[0024] (3) By introducing a reversible epoxy curing system, the obtained thermosetting product is transformed into a thermoplastic above 150 °C and can be used as a production raw material again, thus achieving a material utilization rate close to 100%, and solving the problems of low material utilization rate and high solid waste treatment cost in the prior art.

[0025] (4) The supercritical foaming process can produce products with fine cell structure. On the premise of maintaining the same peel strength, the glue absorption amount is reduced by 30%, solving the technical problem of too high glue absorption amount in the prior art. Detailed Embodiments

[0026] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the claims of the present invention.

[0027] Example 1-1

[0028] The formulation of the rigid crosslinked polyvinyl chloride foam material provided in this example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPa·s), 25 parts of furfurylamine, 20 parts of diphenylmethane bismaleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0029] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this example includes the following steps:

[0030] S1: The chain extender is uniformly added dropwise into the reaction kettle containing epoxy resin within 2 hours and reacted at a temperature of 35°C to obtain modified epoxy resin.

[0031] S2: The raw materials except the foaming agent are fed into the screw extruder through the first feeding port of the automatic feeding machine, and the mixing temperature of the first mixing section of the screw extruder is controlled at 190°C.

[0032] S3: The foaming agent is pressurized to 10.5 Mpa and then fed into the screw extruder through the second feeding port, and the mixing temperature of the second mixing section of the screw extruder is controlled at 160°C.

[0033] S4: The die temperature of the screw extruder is controlled at 135°C, and the extruded material is expanded and foamed.

[0034] S5: The expanded foam is sent into a drying oven at 95°C through a conveyor belt and cured for 3 hours to obtain a one-time formed product.

[0035] Example 1-2

[0036] After crushing 100 parts of the one-time formed product obtained in Example 1-1, the secondary formed product is made according to the following steps:

[0037] It is fed into the screw extruder through the first feeding port, and the mixing temperature of the first mixing section of the screw extruder is controlled at 190°C; 20 parts of the foaming agent carbon dioxide are pressurized to 10.5 Mpa and then fed into the screw extruder through the second mixing section, and the mixing temperature of the second mixing section of the screw extruder is controlled at 160°C; the die temperature of the screw extruder is controlled at 135°C, and the extruded material is expanded and foamed; the expanded foam is sent into a drying oven at 95°C through a conveyor belt and cured for 3 hours to obtain a secondary formed product.

[0038] Example 2-1

[0039] The formula of the rigid crosslinked polyvinyl chloride foam material provided in this example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 30 parts of 2-(2-furyl)ethylamine, 20 parts of diphenylmethane bismaleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0040] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this example is the same as that of Example 1-1.

[0041] Example 2-2

[0042] After crushing 100 parts of the primary formed product obtained in Example 2-1, a secondary formed product is made under the same process conditions as in Example 1-2.

[0043] Example 3-1

[0044] The formula of the rigid crosslinked polyvinyl chloride foam material provided in this example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 25 parts of furfurylamine, 30 parts of bisphenol A diphenyl ether type bismaleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0045] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this example is the same as that of Example 1-1.

[0046] Example 3-2

[0047] After crushing 100 parts of the primary formed product obtained in Example 3-1, a secondary formed product is made under the same process conditions as in Example 1-2.

[0048] Example 4-1

[0049] The formula of the rigid crosslinked polyvinyl chloride foam material provided in this example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 25 parts of furfurylamine, 20 parts of polymeric polyamine type maleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0050] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this example is the same as that of Example 1-1.

[0051] Example 4-2

[0052] After crushing 100 parts of the one-time formed product obtained in Example 4-1, a secondary formed product was made according to the same process conditions as in Example 1-2.

[0053] Comparative Example 1-1

[0054] The formulation of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 25 parts of tetrahydrofurfurylamine, 20 parts of polymeric polyamine type maleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0055] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is the same as that in Example 1-1.

[0056] Comparative Example 1-2

[0057] After crushing 100 parts of the one-time formed product obtained in Comparative Example 1-1, a secondary formed product was made according to the same process conditions as in Example 1-2.

[0058] Comparative Example 2-1

[0059] The formulation of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 25 parts of furfurylamine, 20 parts of N-phenyl maleimide, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0060] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is the same as that in Example 1-1.

[0061] Comparative Example 2-2

[0062] After crushing 100 parts of the one-time formed product obtained in Comparative Example 2-1, a secondary formed product was made according to the same process conditions as in Example 1-2.

[0063] Comparative Example 3

[0064] The formulation of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is as follows: 100 parts of polyvinyl chloride resin SG-3 (degree of polymerization 1250-1350), 70 parts of epoxy resin E51 (viscosity 11200 mPas), 25 parts of furfurylamine, 20 parts of methylhexahydrophthalic anhydride, 20 parts of epoxidized soybean oil, 20 parts of carbon dioxide, and 5 parts of ultrafine calcium carbonate (5-10 μm).

[0065] The preparation process of the rigid crosslinked polyvinyl chloride foam material provided in this comparative example is the same as that in Example 1-1.

[0066] Comparative Example 4

[0067] DIAB commercial product, grade HP60.

[0068] The following performance tests were carried out on the products obtained in the above examples and comparative examples:

[0069] The density test standard is ISO845, and the size is 50*50*50mm; the compression strength / modulus test standard is ISO844, the size is 50×50×50mm, and the speed is 5mm / min; the tensile strength / modulus test standard is ASTM C297, the size is 50×50×50mm, and the speed is 2mm / min; the peel strength test standard is ASTM D1781-98; the cell size is measured with an optical microscope scale, and the statistic is the average value of 200; the resin absorption test size is 500×500×25mm, and the surface density difference is measured after vacuum infusion; the dimensional stability test size is 100×100×25, and the test condition is 120℃ vacuum for 0.5h. The test results are the average values, as shown in the following table.

[0070] The test results of the samples prepared in each example and the commercial DIAB product show that the overall performance of the product prepared by the technical solution provided by the present invention is slightly higher than that of the commercial product, the compression strength is significantly higher than that of the commercial product, and the resin absorption is significantly lower than that of the commercial product. This is because the epoxy crosslinking system used in the technical solution of the present invention has significantly higher strength than the isocyanate crosslinking system of the commercial product; the cell pore diameter of the supercritical foaming system of the present invention is significantly smaller than that of the compression molding foaming system of the commercial product, so the resin absorption is significantly lower than that of the commercial product.

[0071] The test results of the first molding and second molding samples in each example show that the product prepared by the technical solution provided by the present invention is recyclable, and the performance of the prepared product does not decrease after recycling.

[0072] The test results of the samples in each example and Comparative Examples 1, 2, and 3 show that only by using the chain extender and curing agent provided by the present invention can a product with a reversible crosslinked structure be prepared. The samples in Comparative Examples 1 and 2 cannot be crosslinked, so the performance drops significantly; the sample in Comparative Example 3 can only be partially crosslinked in the same production cycle, and the performance drops significantly while it cannot be reprocessed. The activity of other types of epoxy curing agents is much higher than that of anhydrides, and they cannot be used as the main crosslinking system in the technical field of this product.

[0073] Table 1

[0074]

[0075]

[0076] In summary, the overall performance of the product prepared by the technical solution provided by the present invention is comparable to that of commercially available products, and the compression strength and resin absorption amount are significantly better than those of commercially available products; the production cycle of the product is only a few hours, far lower than 15 - 20 days of the prior art, and the production efficiency is greatly improved; the product can be recycled, solving the technical problems of large amount of solid waste and high treatment cost in this industry.

Claims

1. A recyclable rigid crosslinked polyvinyl chloride foam material, characterized in that, Its raw materials are composed by mass parts as follows:

2. The recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, characterized in that: The degree of polymerization of the polyvinyl chloride is 1000 - 5000.

3. The recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, characterized in that: The epoxy resin is at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin with a viscosity of 1000 - 20000 mPa·s.

4. A recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, characterized in that: The chain extender is a compound with a chemical structure as shown in formula (1), where R1 is at least one of C1-C 20 alkyl, aryl, and cycloalkyl groups:

5. The recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, wherein: The plasticizer is at least one of epoxy soybean oil, epoxy methyl ester, and epoxy fatty acid methyl ester.

6. The recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, wherein: The foaming agent is at least one of cyclopentane, carbon dioxide, and nitrogen.

7. A recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, characterized in that: The reversible curing agent is at least one of maleimide compounds containing no less than 2 maleimide groups and having a molecular weight of 200 - 12000.

8. A recyclable rigid crosslinked polyvinyl chloride foam material according to claim 1, characterized in that: The nucleating agent is at least one of titanium dioxide, calcium carbonate, magnesium carbonate, and silicon dioxide with a particle size not greater than 10 microns.

9. A method for preparing the recyclable rigid crosslinked polyvinyl chloride foam material according to any one of claims 1 to 8, characterized in that, It is carried out according to the following steps: S1: The chain extender is uniformly dropped into the reaction kettle containing epoxy resin within 1 - 3 h and reacts at a temperature of 20 - 40 °C to obtain modified epoxy resin. S2: The raw materials except the foaming agent are fed into the screw extruder through the first feeding port of the automatic feeding machine, and the mixing temperature of the first mixing section of the screw extruder is controlled between 180 - 200 °C. S3: The foaming agent is pressurized to 5 - 15 Mpa and then fed into the screw extruder through the second feeding port, and the mixing temperature of the second mixing section of the screw extruder is controlled between 150 - 180 °C. S4: The die temperature of the screw extruder is controlled at 110 - 140 °C, and the extruded material is expanded and foamed. S5: The expanded foam is fed into a drying oven at 90 - 110 °C through a conveyor belt and cured for 1 - 3 h to obtain the product.

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